In the investigative work of the use of polyvalent Group IV metallic ions as tags for identifying reactive sites of cotton it was learned that the most reactive ion was plumbite which added up to 40% by weight of Pb, as compared to 5% or less for other metals. It was further learned that placing the plumbite-treated cotton sample in a glass dish and heating in an oven at about 600.degree. C., for about 1 hour, produced a glasslike material. It was unexpectedly discovered that the similarity to the work with other ions had ceased. Although the treated cotton fabric retained its structural integrity the treated fabric when removed from the oven exhibited a glassy appearance. It was found to be harder than soft glass or stainless steel. The surface smoothness and adherence to the glass dish depended on the percent of plumbite in the cotton intermediate. Low plumbite contents, say 5% to 15%, caused firm adhesion and a less smooth surface than with plumbite contents above 15%.
Further investigative work indicated that to form the new glassy material the plumbite-treated fabric intermediate needs to be in contact with a high silicon content surface when heated. It was also learned that the heating needs to take place in an atmosphere with limited oxygen present. An essential part of the process is that the high-silicon surface and the oven be at a temperature below 200.degree. C. when placed in contact with the treated fabric. Higher temperatures burn the fabric and destroy the process. The glassy material thus produced resists acids and alkalis. It was also learned that this treatment can be adjusted by using a low plumbite content in the intermediate to produce a surface upon which identification markings can be made with a lead pencil. The markings can be removed by erasure with a rubber eraser. It was also found that the adhesive property can be used to form a glasslike weld between glasses and/or ceramic articles. Of particular interest was the welding of unlike glasses, such as soft and hard glass or porcelain and hard glass by the process of this invention. Such welds are difficult to achieve by use of prior art.
It was further found by investigation that cellulosic materials other than cotton can be used provided hydroxyl groups are available for adding the plumbite ion. It was also found that powdered cellulosic material may be used. It was further established that neither lead monoxide alone nor lead monoxide admixed either with the cellulosic material or with carbon will produce the glasslike material described as the product of this invention.
Prior art processes are known for adding a glaze to ceramic objects by applying a metal oxide paste or paint and prior art processes are known for treating materials with sodium plumbite.
In contrast to the prior art, this invention relates to a process whereby the metallic ion is reacted with a cellulosic material to produce a stable intermediate. This intermediate is essential to the process of this invention and is preferably used as a fabric or other fibrous material although it can be used as powder. It is this intermediate that when heated in contact with a surface containing silicon produces the glasslike material. In contrast to the glaze of prior art the glasslike material of this invention reveals the structure and texture of the intermediate, which has become transparent or translucent. In contrast to the glaze of prior art this material contains carbon indicating the presence of some structural fingerprint of the cellulosic intermediate material.
The literature discloses that R. C. Griffin (Technical Methods of Analysis, McGraw Hill, Inc., N.Y. (1927) had a method of preparing sodium plumbite solutions at 26.degree. C. without constant shaking. Griffin does not specify an exact time for the contact between the lead monoxide and a sodium hydroxide solution prior to filtering. He does suggest that at least 24 hours be observed, with occasional shaking.
The revelations of Griffin were scrutinized and used as a basis for further investigative work. A full report of this investigative work by the instant inventors appears in Textile Research Journal, pp. 12-21, January 1974, the article bearing the title "Addition of Lead from Sodium Plumbite Solution to Modified and Unmodified Cottons". It should be pointed out that although sodium hydroxide is used because of its availability, in the preparation of the plumbite solutions of this invention, other suitable alkali metal hydroxides would be expected to yield similar results.